/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.transforms.join;



import com.bff.gaia.unified.sdk.Pipeline;

import com.bff.gaia.unified.sdk.coders.Coder;

import com.bff.gaia.unified.sdk.coders.KvCoder;

import com.bff.gaia.unified.sdk.transforms.PTransform;

import com.bff.gaia.unified.sdk.values.*;

import com.bff.gaia.unified.vendor.guava.com.google.common.collect.ImmutableMap;

import com.bff.gaia.unified.sdk.values.KV;

import com.bff.gaia.unified.sdk.values.PCollection;

import com.bff.gaia.unified.sdk.values.PInput;

import com.bff.gaia.unified.sdk.values.POutput;

import com.bff.gaia.unified.sdk.values.PValue;

import com.bff.gaia.unified.sdk.values.TupleTag;

import com.bff.gaia.unified.sdk.values.TupleTagList;



import javax.annotation.Nullable;

import java.util.ArrayList;

import java.util.List;

import java.util.Map;



/**

 * An immutable tuple of keyed {@link PCollection PCollections} with key type K. ({@link PCollection

 * PCollections} containing values of type {@code KV<K, ?>})

 *

 * @param <K> the type of key shared by all constituent PCollections

 */

public class KeyedPCollectionTuple<K> implements PInput {

  /** Returns an empty {@code KeyedPCollectionTuple<K>} on the given pipeline. */

  public static <K> KeyedPCollectionTuple<K> empty(Pipeline pipeline) {

    return new KeyedPCollectionTuple<>(pipeline);

  }



  /** Returns a new {@code KeyedPCollectionTuple<K>} with the given tag and initial PCollection. */

  public static <K, InputT> KeyedPCollectionTuple<K> of(

	  TupleTag<InputT> tag, PCollection<KV<K, InputT>> pc) {

    return new KeyedPCollectionTuple<K>(pc.getPipeline()).and(tag, pc);

  }



  /**

   * A version of {@link #of(TupleTag, PCollection)} that takes in a string instead of a TupleTag.

   *

   * <p>This method is simpler for cases when a typed tuple-tag is not needed to extract a

   * PCollection, for example when using schema transforms.

   */

  public static <K, InputT> KeyedPCollectionTuple<K> of(String tag, PCollection<KV<K, InputT>> pc) {

    return of(new TupleTag<>(tag), pc);

  }



  /**

   * Returns a new {@code KeyedPCollectionTuple<K>} that is the same as this, appended with the

   * given PCollection.

   */

  public <V> KeyedPCollectionTuple<K> and(TupleTag<V> tag, PCollection<KV<K, V>> pc) {

    if (pc.getPipeline() != getPipeline()) {

      throw new IllegalArgumentException("PCollections come from different Pipelines");

    }

    TaggedKeyedPCollection<K, ?> wrapper = new TaggedKeyedPCollection<>(tag, pc);

    Coder<K> myKeyCoder = keyCoder == null ? getKeyCoder(pc) : keyCoder;

    List<TaggedKeyedPCollection<K, ?>> newKeyedCollections = copyAddLast(keyedCollections, wrapper);

    return new KeyedPCollectionTuple<>(

        getPipeline(), newKeyedCollections, schema.getTupleTagList().and(tag), myKeyCoder);

  }



  /**

   * A version of {@link #and(String, PCollection)} that takes in a string instead of a TupleTag.

   *

   * <p>This method is simpler for cases when a typed tuple-tag is not needed to extract a

   * PCollection, for example when using schema transforms.

   */

  public <V> KeyedPCollectionTuple<K> and(String tag, PCollection<KV<K, V>> pc) {

    return and(new TupleTag<>(tag), pc);

  }



  public boolean isEmpty() {

    return keyedCollections.isEmpty();

  }



  /**

   * Returns a list of {@link TaggedKeyedPCollection TaggedKeyedPCollections} for the {@link

   * PCollection PCollections} contained in this {@link KeyedPCollectionTuple}.

   */

  public List<TaggedKeyedPCollection<K, ?>> getKeyedCollections() {

    return keyedCollections;

  }



  /**

   * Like {@link #apply(String, PTransform)} but defaulting to the name provided by the {@link

   * PTransform}.

   */

  public <OutputT extends POutput> OutputT apply(

      PTransform<KeyedPCollectionTuple<K>, OutputT> transform) {

    return Pipeline.applyTransform(this, transform);

  }



  /**

   * Applies the given {@link PTransform} to this input {@code KeyedPCollectionTuple} and returns

   * its {@code OutputT}. This uses {@code name} to identify the specific application of the

   * transform. This name is used in various places, including the monitoring UI, logging, and to

   * stably identify this application node in the job graph.

   */

  public <OutputT extends POutput> OutputT apply(

      String name, PTransform<KeyedPCollectionTuple<K>, OutputT> transform) {

    return Pipeline.applyTransform(name, this, transform);

  }



  /**

   * Expands the component {@link PCollection PCollections}, stripping off any tag-specific

   * information.

   */

  @Override

  public Map<TupleTag<?>, PValue> expand() {

    ImmutableMap.Builder<TupleTag<?>, PValue> retval = ImmutableMap.builder();

    for (TaggedKeyedPCollection<K, ?> taggedPCollection : keyedCollections) {

      retval.put(taggedPCollection.tupleTag, taggedPCollection.pCollection);

    }

    return retval.build();

  }



  /**

   * Returns the key {@link Coder} for all {@link PCollection PCollections} in this {@link

   * KeyedPCollectionTuple}.

   */

  public Coder<K> getKeyCoder() {

    if (keyCoder == null) {

      throw new IllegalStateException("cannot return null keyCoder");

    }

    return keyCoder;

  }



  /** Returns the {@link CoGbkResultSchema} associated with this {@link KeyedPCollectionTuple}. */

  public CoGbkResultSchema getCoGbkResultSchema() {

    return schema;

  }



  @Override

  public Pipeline getPipeline() {

    return pipeline;

  }



  private static <K, V> Coder<K> getKeyCoder(PCollection<KV<K, V>> pc) {

    // TODO: This should already have run coder inference for output, but may not have been consumed

    // as input yet (and won't be fully specified); This is fine



    // Assumes that the PCollection uses a KvCoder.

    Coder<?> entryCoder = pc.getCoder();

    if (!(entryCoder instanceof KvCoder<?, ?>)) {

      throw new IllegalArgumentException("PCollection does not use a KvCoder");

    }

    @SuppressWarnings("unchecked")

    KvCoder<K, V> coder = (KvCoder<K, V>) entryCoder;

    return coder.getKeyCoder();

  }



  /////////////////////////////////////////////////////////////////////////////



  /** A utility class to help ensure coherence of tag and input PCollection types. */

  public static class TaggedKeyedPCollection<K, V> {



    final TupleTag<V> tupleTag;

    final PCollection<KV<K, V>> pCollection;



    public TaggedKeyedPCollection(TupleTag<V> tupleTag, PCollection<KV<K, V>> pCollection) {

      this.tupleTag = tupleTag;

      this.pCollection = pCollection;

    }



    /** Returns the underlying PCollection of this TaggedKeyedPCollection. */

    public PCollection<KV<K, V>> getCollection() {

      return pCollection;

    }



    /** Returns the TupleTag of this TaggedKeyedPCollection. */

    public TupleTag<V> getTupleTag() {

      return tupleTag;

    }

  }



  /** We use a List to properly track the order in which collections are added. */

  private final List<TaggedKeyedPCollection<K, ?>> keyedCollections;



  @Nullable

  private Coder<K> keyCoder;



  private final CoGbkResultSchema schema;



  private final Pipeline pipeline;



  KeyedPCollectionTuple(Pipeline pipeline) {

    this(pipeline, new ArrayList<>(), TupleTagList.empty(), null);

  }



  KeyedPCollectionTuple(

      Pipeline pipeline,

      List<TaggedKeyedPCollection<K, ?>> keyedCollections,

      TupleTagList tupleTagList,

      @Nullable Coder<K> keyCoder) {

    this.pipeline = pipeline;

    this.keyedCollections = keyedCollections;

    this.schema = new CoGbkResultSchema(tupleTagList);

    this.keyCoder = keyCoder;

  }



  private static <K> List<TaggedKeyedPCollection<K, ?>> copyAddLast(

      List<TaggedKeyedPCollection<K, ?>> keyedCollections,

      TaggedKeyedPCollection<K, ?> taggedCollection) {

    List<TaggedKeyedPCollection<K, ?>> retval = new ArrayList<>(keyedCollections);

    retval.add(taggedCollection);

    return retval;

  }

}